only milk

Milk is defined as the whole, fresh, clean lacteral secretion obtained by the complete milking of one or more healthy milch animals, such as cows, buffaloes, goats, and sheep.
It excludes milk obtained within 15 days before and 5 days after calving, known as colostrum, which has distinct physical, chemical, and biological properties.

The freezing point of milk is lower than that of water (e.g., cow milk: 0.547 °C & buffalo milk: 0.549 °C).
A freezing point test can reveal abnormalities; for instance, adding water increases the freezing point.

Milk ranges from creamish white to yellowish cream with a bluish tinge due to colloidal particles.

The flavor of milk comes from a mix of sweet lactose, salty minerals, and the characteristic taste of casein.

The physical and chemical properties of milk can change due to the condition of the animal, food type, stage of lactation, and season. Pronounced changes are typically regarded as abnormal.

Milk is sterile when secreted but can become contaminated during milking and handling.
The types of microorganisms in milk vary greatly depending on contamination sources throughout production and storage.

Mesophiles: Grow optimally at around 30°C; includes species like Micrococcus, Staphylococcus, and various lactic acid bacteria.
Thermophiles: Thrive at higher temperatures (up to 70°C) and survive pasteurization; includes species such as B. stearothermophilus.
Thermodurics: Can survive pasteurization but will not grow at those temperatures; examples include Micrococcus caseolyticus.
Psychrotrophs: Prefer temperatures below 20°C and can grow in refrigeration; examples include Pseudomonas and Enterobacter.
Pathogens: Can enter milk from diseased animals, handlers, and environmental sources, with notable examples such as Brucella and Salmonella.

Bactericidal Stage: Milk contains antimicrobial substances that prevent microbial growth temporarily.
Development of Mixed Microflora: Following the bactericidal stage, lactic acid bacteria dominate.
Growth of Yeast and Mold: After lactic bacteria die, yeast and mold may proliferate, converting acids back into simpler compounds.
Growth of Proteolytic Bacteria: Eventually leads to spoilage, producing off-flavors and denaturing milk compositions.

Mastitis is an inflammation of the udder often of microbial origin, resulting in high somatic cell counts and altered properties in the milk.
Common causative agents include Streptococcus agalactiae and Staphylococcus aureus. Mastitis milk shows:
- Increased levels of whey proteins, salts, and enzymes.
- Decreased lactose, fat, and total casein levels.

Symptoms include higher pH, chlorides, and somatic cell counts; specific tests include:
- Blue and Bromothymol tests: Indicate pH abnormalities.
- SLS Test: Assesses somatic cell count.
- Microscopic Examination: Identifies bacterial presence in milk.

Sampling must be representative, aseptic, and appropriately labeled. Transport should be at controlled temperatures to prevent microbial growth.

Rapid Platform Tests (RPT) and organoleptic tests assess microbial contamination levels based on milk's characteristics.
Specific tests include Clot on Boiling, Sediment, Alcohol, pH and titratable acidity, and dye reduction tests.

Indian Standards detail acceptable microbial counts in raw and pasteurized milk, using methods like Direct Microscopic Count, Standard Plate Count, and Methylene Blue Reduction Test to classify the quality from Very Good to Poor.

Defined as the heat processing of milk intended to destroy pathogens while maintaining nutritional quality. Various methods include LTLT, HTST, and Flash processes.
Effects of Pasteurization: While it successfully kills pathogens, it may also reduce certain nutritional components and occasionally allow thermodurics to survive.

Starter cultures are specific microbes added to milk for fermentation, enhancing flavor and preservation in dairy products like cheese and yogurt, primarily through acid production.

Includes various strains of Lactic Acid Bacteria (LAB), molds, and yeasts, with roles in developing flavor, texture, and safety profiles for fermented products.